Lysosomal integral membrane protein II binds thrombospondin-1. Structure-function homology with the cell adhesion molecule CD36 defines a conserved recognition motif.
LIMPII (lysosomal integral membrane protein II) is one of a family of proteins structurally related to the cell surface glycoprotein CD36. We recently defined a single structural domain on CD36 that mediates binding to adhesive glycoprotein thrombospondin-1 (TSP1). The CD36-TSP1 interaction is known to play a role in platelet-tumor and platelet-monocyte adhesion, angiogenesis, and in monocyte uptake of apoptotic cells. To test whether LIMPII also binds TSP1, a LIMPII peptide corresponding to the TSP1 binding domain of CD36 was expressed as a recombinant glutathione S-transferase (GST) fusion protein. In solid phase binding assays, purified 125I-TSP1 bound to immobilized GST/LIMPII in a time-dependent and saturable manner. Inhibition by excess unlabeled TSP1 or EDTA demonstrated specificity. LIMPII.TSP1 complex formation was specifically blocked by soluble LIMPII fusion protein, by monospecific rabbit IgG directed against the LIMPII peptide and by CD36 fusion proteins containing the TSP1 binding domain. Transfection of Bowes melanoma cells with a chimeric LIMPII cDNA that targets expression to the plasma membrane conferred the ability to bind 125I-TSP1 and to adhere to TSP1-coated surfaces. This study defines a TSP1 binding site conserved between LIMPII and CD36 and suggests that cell surface LIMPII may function in some circumstances as an adhesion receptor for TSP1. Computer-assisted homology searches suggest that the TSP1 recognition motif identified from study of CD36 family members may be widely expressed in nature.
Crombie
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Program in Cell Biology and Genetics, Cornell University Graduate School of Medical Sciences, Cornell University Medical College, New York, New York 10021, USA.
Silverstein
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D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D002451:Cell Compartmentation; D017124:Conserved Sequence; D019143:Evolution, Molecular; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes; D008546:Melanoma, Experimental; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins; D017386:Sequence Homology, Amino Acid; D019700:Thrombospondin 1 / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D018955:CD36 Antigens; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D019700:Thrombospondin 1; C070693:Scarb2 protein, rat